The invention relates to an apparatus for molding articles, wherein the apparatus includes mold sections that are forcefully biased together by ambient air pressure.
A common method of thermoforming articles is compression molding. For example, compression molding is used to make headliners that cover the interior surface of a motor vehicle roof.
A typical apparatus used in compression molding headliners includes a pair of relatively thick mold halves that are forced together by a press. Known mold halves comprising metal are relatively heavy and expensive to manufacture. On the other hand, mold halves comprising epoxy require a considerable amount of time to cool. As a result, cycle time per part is significant. Furthermore, the press used to compress such mold halves together is relatively large and expensive.
U.S. Pat. No. 4,327,049 discloses another apparatus for making headliners that includes a mold having a pair of thermally regulated mold halves. These mold halves have a plurality of passages through which coolant fluid is routed to adequately cool the mold. Consequently, this apparatus is costly to manufacture and use.
The present invention addresses the shortcomings of the prior art by providing a low cost apparatus for forming articles, such as headliners, from at least one layer of formable material. The apparatus includes a mold for receiving the at least one layer of formable-material. The mold has first and second thin mold sections and a seal associated with at least one of the mold sections for effecting a sufficiently sealed relationship between the mold sections. Each mold section has a non-planar configuration, and one mold section has at least one aperture. A vacuum source is in fluid communication with the at least one aperture for applying a vacuum pressure to the at least one aperture when the mold sections are sufficiently sealed together in order to reduce air pressure within the mold. As a result, ambient air pressure is used to forcefully bias the mold sections sufficiently together so as to form the at least one layer of formable material to a contour corresponding to the non-planar configurations of the mold sections. Furthermore, each mold section is sufficiently rigid such that the mold sections do not substantially flex when the mold sections are forcefully biased together.
While the seal may have any suitable configuration and comprise any suitable material, in one embodiment of the apparatus, the seal comprises a flange portion formed as part of one of the mold sections. The flange portion is configured to overlap the other mold section when the mold sections are moved sufficiently close together. Alternatively or supplementally, the seal may also comprise a compressible seal and/or a blade seal attached to one or both of the mold sections.
One mold section may also have a peripheral channel in communication with the at least one aperture. Such a channel enables a vacuum to initially be drawn along the periphery of the mold, which is particularly advantageous in the event the article comprises substantially impermeable materials.
A portion, such as a peripheral portion, of at least one of the mold sections may comprise a flexible material. Such a design is advantageous, for example, in forming rounded edges or other features on the article.
In one embodiment of the apparatus, the mold sections are pivotally connected together such that at least one mold section is pivotable toward the other mold section. In this embodiment, the mold is preferably provided with a locator for aligning the mold sections as the at least one mold section is pivoted toward the other mold section. The locator includes a locating pin assembly connected to the first mold section, and a receptacle connected to the second mold section. Furthermore, the locating pin assembly includes a bullet-shaped locating pin that is engageable with the receptacle.
The locating pin assembly may also include a housing for receiving the locating pin such that the locating pin is moveable with respect to the housing. With such a configuration, the at least one mold section may continue to pivot toward the other mold section after the locating pin has engaged the receptacle.
Additionally, the locator preferably functions as a mold stop. For example, the housing may be provided with a first engaging surface, and the receptacle may be provided with a second engaging surface engageable with the first engaging surface. When the engaging surfaces are engaged with each other, pivotal movement of the at least one mold section toward the other mold section is inhibited.
Preferably, the mold further includes a mold gap measurement device for determining gap thickness between the mold sections. The mold gap measurement device may include, for example, a magnet connected to one mold section, and a magnetic force detection device connected to the other mold section.
The apparatus may also comprise a controller in communication with the mold gap measurement device and the vacuum source. The controller is preferably operable to control the vacuum pressure applied by the vacuum source based on the gap thickness between the mold sections.
Furthermore, the apparatus may include a heating device for heating the at least one layer of formable material, and one of the mold sections may include at least one temperature measurement device in communication with the heating device for determining temperature of a portion of the at least one layer of formable material. With such an arrangement, the heating device may be controlled based on temperature readings provided by the at least one temperature measurement device.
Further under the invention, an apparatus for forming an article from at least one layer of formable material includes a mold for receiving the at least one layer of formable material. The mold has first and second mold sections pivotally connected together, and a compressible seal disposed between the mold sections. Each mold section has a non-planar configuration, and one mold section has at least one aperture and a peripheral channel in communication with the at least one aperture. A vacuum source is in fluid communication with the at least one aperture and the channel for reducing air pressure within the mold. As a result, ambient air pressure is used to forcefully bias the mold sections sufficiently together and compress the seal, so as to form the at least one layer of formable material to a contour corresponding to the non-planar configurations of the mold sections. Each mold section is sufficiently rigid such that the mold sections do not substantially flex when the mold sections are forcefully biased together.
More specifically, an apparatus according to the invention for forming an article from at least one layer of formable material includes a frame assembly having first and second frame portions. The frame portions are pivotally connected together such that at least one of the frame portions is pivotable with respect to the other frame portion between an open position and a closed position. The frame assembly further includes an inflatable device connected to the first frame portion. The apparatus also includes a mold for receiving the at least one layer of formable material. The mold includes first and second mold sections and a seal associated with at least one of the mold sections. The first mold section is cooperable with the inflatable device such that the first mold section is moveable with respect to the first frame portion upon inflation of the inflatable device. The second mold section is connected to the second frame portion. Each mold section has a non-planar configuration, and one mold section has at least one aperture. A vacuum source in fluid communication with the at least one aperture. When the at least one frame portion is in the closed position, the inflatable device is operable for moving the first mold section toward the second mold section to effect a sufficiently sealed relationship between the mold sections. Furthermore, the vacuum source is operable for reducing air pressure within the mold to thereby cause ambient air pressure to forcefully bias the mold sections sufficiently together so as to form the at least one layer of formable material to a contour corresponding to the non-planar configurations of the mold sections. Each mold section is sufficiently rigid such that the mold sections do not substantially flex when the mold sections are forcefully biased together.
Numerous applications for the present invention are contemplated. For example, the present invention may be used to secure a cover member to a preheated plastic sheet while forming the plastic sheet. Furthermore, the invention may be used with both thermosets and thermoplastic materials.
These and other objects, features and advantages of the invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in conjunction with the accompanying drawings.